Improve behaviour when we hit a stack overflow / OOM error

runtime/vm/exceptions.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/exceptions.h"
 
 #include "platform/address_sanitizer.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
@@ skipping 46 matching lines @@
   const GrowableObjectArray& pc_offset_list_;
 
   DISALLOW_COPY_AND_ASSIGN(RegularStacktraceBuilder);
 };
 
 
 class PreallocatedStacktraceBuilder : public StacktraceBuilder {
  public:
   explicit PreallocatedStacktraceBuilder(const Instance& stacktrace)
   : stacktrace_(Stacktrace::Cast(stacktrace)),
-        cur_index_(0) {
+        cur_index_(0),
+        dropped_frames_(0) {
     ASSERT(stacktrace_.raw() ==
            Isolate::Current()->object_store()->preallocated_stack_trace());
   }
   ~PreallocatedStacktraceBuilder() { }
 
   virtual void AddFrame(const Code& code, const Smi& offset);
 
  private:
   static const int kNumTopframes = Stacktrace::kPreallocatedStackdepth / 2;
 
   const Stacktrace& stacktrace_;
   intptr_t cur_index_;
+  intptr_t dropped_frames_;
 
   DISALLOW_COPY_AND_ASSIGN(PreallocatedStacktraceBuilder);
 };
 
 
 void PreallocatedStacktraceBuilder::AddFrame(const Code& code,
                                              const Smi& offset) {
   if (cur_index_ >= Stacktrace::kPreallocatedStackdepth) {
     // The number of frames is overflowing the preallocated stack trace object.
     Code& frame_code = Code::Handle();
     Smi& frame_offset = Smi::Handle();
     intptr_t start = Stacktrace::kPreallocatedStackdepth - (kNumTopframes - 1);
     intptr_t null_slot = start - 2;
+    // We are going to drop one frame.
+    dropped_frames_++;
     // Add an empty slot to indicate the overflow so that the toString
     // method can account for the overflow.
     if (stacktrace_.FunctionAtFrame(null_slot) != Function::null()) {
       stacktrace_.SetCodeAtFrame(null_slot, frame_code);
+      // We drop an extra frame here too.
+      dropped_frames_++;
     }
+    // Encode the number of dropped frames into the pc offset.
+    frame_offset ^= Smi::New(dropped_frames_);
+    stacktrace_.SetPcOffsetAtFrame(null_slot, frame_offset);
     // Move frames one slot down so that we can accomodate the new frame.
     for (intptr_t i = start; i < Stacktrace::kPreallocatedStackdepth; i++) {
       intptr_t prev = (i - 1);
       frame_code = stacktrace_.CodeAtFrame(i);
       frame_offset = stacktrace_.PcOffsetAtFrame(i);
       stacktrace_.SetCodeAtFrame(prev, frame_code);
       stacktrace_.SetPcOffsetAtFrame(prev, frame_offset);
     }
     cur_index_ = (Stacktrace::kPreallocatedStackdepth - 1);
   }
@@ skipping 550 matching lines @@
   }
 
   return DartLibraryCalls::InstanceCreate(library,
                                           *class_name,
                                           *constructor_name,
                                           arguments);
 }
 
 
 }  // namespace dart